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    <script>
        //逻辑与
        //1表达式为真则返回表达式为2    ，1表达式为假的，则返回表达式1
        console.log(123 && 456); //456
        console.log(0 && 456); //0
        //*************************************************
        //逻辑或
        //表达式1为真则返回表达式1，    表达式1为假，则返回表达式2
        console.log(123 || 0); //123
        console.log(0 || 123); //123
    </script>
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